Switched mode power supplies are preferred over linear voltage regulators in RFID readers because of their power conversion efficiency and ability to produce voltage of both positive and negative polarities. However, due to rapid changes in energy flow at switching instants, switched mode power supplies produce spike-like noise. The spike-like noise at the switching instants have spectral energy that overlaps with the RFID signal response thereby degrading the signal to noise ratio (SNR) of the reader.